This invention relates generally to the field of surgical instrumentation, and more particularly, to an insufflating device adapted for use in pneumatically expanding the uterus for intrauterine surgical procedures. Prior art devices of this type have included a relatively rigid hollow shaft, the outer surface of which mounts an inflatable balloon, which serves to distend the uterine walls. The end of the shaft is open, and permits the insertion of an endoscopic or cystoscopic instrument. Unfortunately, the performance of such devices has left much to be desired. Because the working area of the single balloon is generally below the end of the rigid tube, the upper end of the uterus must be distended by introducing unconfined air or other fluid which distends the uterus by virtue of the fact that the cervix is made fluid tight. However, the pressurized fluid is thereby forced into the fallopian tubes, with resultant frequent formation of embolisms and similar complications.